Drive control for motorized hand lift trucks



March 11, 1952 1. F. SCHRECK DRIVE CONTROL FOR MOTORIZED HAND LIFTTRUCKS 2 SHEETSSHEET 1 Filed Sept. 27, 1946 Irvin, E Schrecla INVENTORMarch 11, 1952 1. F. SCHRECK DRIVE CONTROL FOR MOTORIZED HAND LIFTTRUCKS Filed Sept. 27, 1946 2 SHEETSSHEET 2 INVENTOR Vin, 'E SchreckCir/a1: 7 20 ATTORNEYS z Patented Mar. 11, 1952 DRIVE CONTROL FORMOTORIZED HAND LIFT TRUCKS Irvin F. Schreck, Cleveland Heights, OhioApplication September 27, 1946, Serial No. 699,691

3 Claims. 1

This invention relates to a drive control for trucks of the type shownin my Patent No. 2,209,356, granted July 30, 1940 and known as motorizedhand lift trucks, these trucks being provided with a vertically swingingdraft tongue that is connected to a swiveled steering wheel framelocated at the front end of the truck and carrying a front supportingwheel and a propelling motor that is controlled by manually operablecontrol elements on the draft tongue and by movements of the drafttongue which stops the motor and applies a brake when swung to verticalposition.

The invention has for one of its principal objects to provide a controldevice on the tongue which is manually operable to start, stop and varythe speed of the motor in any of the angular positions of the tongue soas to provide for convenient manipulation of the truck in restrictedspaces.

An additional object is to provide a simple speed varying device for anelectric propelling motor that can be readily applied to single speedmotors in use on such trucks.

A further object of the invention is to provide a control that isoperated by turning the tongue hand grip about its axis in one directionor the other from a neutral position and which is operable to start themotor in low speed in either direction and to increase or decrease thespeed at will during operation.

With the above and other objects in view, the invention may be said tocomprise the control mechanism illustrated in the accompanying drawings,hereinafter described and particularly set forth in the appended claims,together with such variations and modifications thereof as will beapparent to one skilled in the art to which the invention pertains.

Reference should be had to the accompanying drawings forming a part ofthis specification in which:

Figure 1 is a fragmentary side elevation of a front end of a truck towhich the invention is applied;

Fig. 2 is a rear elevation of the propelling motor;

Fig. 3 is a longitudinal section through the motor control mounted onthe draft tongue;

Fig. 4 is a transverse section taken on the line indicated at 44 in Fig.3;

Figs. 5 and 6 are sectional views similar to Fig. 3, Fig. 5 showing thecontrol in one of its slow speed positions and Fig. 6 showing thecontrol in one of its high speed positions; and

Fig. '7 is a wiring diagram showing the motor control circuits.

The accompanying drawings show the front end only of an industrialtruck, the truck frame being indicated by the numeral I and having aswiveled frame 2 mounted at the front end thereof to turn about avertical axis. The frame 2 has a front supporting wheel 3 mountedtherein and carries a propelling motor 4 which drives the wheel 3through a sprocket chain 5. A draft tongue 6 is connected to theswiveled frame 2 by means of a horizontal pivot 1 and can be used eitherto steer the truck while it is being propelled, or for pushing orpulling the truck manually.

The motor 4 is preferably an electric motor provided with suitablecontrol switches and supplied with current from a suitable source suchas a battery mounted on an adjacent portion of the truck, current beingsupplied to the motor by a conductor cable 8 through a safety switch 9which is normally closed but which carries an abutment ID in the path ofmovement of the tongue 6 by means of which the switch is opened by thetongue when the tongue is moved to vertical position. The safety switchis shown in more detail in my copending application Serial No. 547,930,filed August 3, 1944, now Patent 2,478,327 issued August 9, 1949. Theswitch 9 is closed whenever the tongue (5 is moved out of engagementwith the abutment II], so that the motor 4 is operable in any of theinclined positions of the tongue under the control of manually operablemeans carried by the tongue. The motor 4 is mounted upon a housing IIthat encloses solenoids I2 and I3 which control the forward and reverseactuation of the motor.

The present invention provides a change speed device in the form of aunit which may be at tached externally to the motor casing. The changespeed unit comprises a carbon rod resistance I 4 adapted to beinterposed in the circuit of either the forward or reverse winding ofthe motor 4, whichever is energized, and a solenoid I5 by means of whichthe resistance is controlled. Wires I6, I! and I8 extend from oneterminal of each of the three solenoids I2, I3 and I5 through the tongue6, which may be of tubular form, to terminals I9, 29 and 2| carried byan elongated cylindrical block 22 attached to the tongue 6 adjacent itsouter end. Energizing contacts 23 and 24 are connected to the terminalsI9 and 20 for controlling the solenoids I2 and I3 and an energizingcontact 25 is connected to the terminal 2! for controlling the solenoidI5. A grounding element 26 is positioned above the contacts 23, 24 and25 and is movable endwise to energize the solenoids I2, I3 and I in theproper sequence. The element 26 is preferably in the form of a metalmember attached to a shaft 21 that is positioned parallel to the tongue6 and slidably mounted in lugs 28 and 29 that are suitably secured tothe top of the tongue '6. The grounding member 26 is normally held inthe neutral position by means of coil springs 36 and 3| which areinterposed between opposite ends of the member 26 and the lugs 28 and29. The switch elementsabove referred to are enclosed within a housing32 which also serves as an actuating member, the housing 32 having aninner end wall 33 through which the inner end of the'shaft 21 extendsand to which the shaft 21 is anchored by means of collars 34 and 35attached to the shaft 21 inside and outside the wall 33. The outer endof the-housing member 32 is connected by a horizontal pivot 36 to lugs31 carried by hand grip sleeves 38. The lugs 31 are positioned uponopposite sides of the outer end of the member 32, and the sleeves 33 arerotatably mounted on tubular handle members 39 welded or otherwiserigidly secured to the outer end of the tongue 6 and disposed at rightangles to the tongue. The hand grip sleeves 38 are mounted between thetongue 6 and retaining collars 45 attached to the outer ends of themembers 39. Each of the hand grip sleeves may be provided with a thumblug 4| to assist in turning it.

The grounding member 26 is provided with end contact portions 42 and 43which are spaced apart 42-and 43 are of a length such that each remainsin engagement with its energizing contact throughout the extent ofendwise movement of the grounding member. The engagement of the contactmember 42 with the contact member 23 energizes the solenoid I2 to propelthe motor forwardly, and engagement of the contact portion 42 with thecontact 24 energizes the solenoid 13 to propel the truck rearwardly.

Intermediate the contact portions 42 and 43 the member 26 has shortengaging lugs 44 and 45 that are engageable with the intermediatecontact 25. In the neutral position of the member 26 shown in Fig. 3,the lugs 44 and 45 are on opposite sides of the contact 25 and out ofengagement therewith. Engagement of either the lug 44 or 45 with thecontact 25 serves to place the resistance I4 in series with theenergized winding of the motor to reduce the speed of the motor ineither direction, and the lugs 44- and 45 are spaced from the contact 25substantially the same distance as the contact portions 42 and 43 fromthe contacts 23 and 24 when the member 26 is in neutral position, sothat one of the lugs 44 or 45 engages the contact 25 simultaneously withthe engagement of the contact 23 or 24 with the contact portions 42 or43, so that the motor is started in either direction at a low speed.Continued movement of the member 26 in either direction causes the lug44 or 45, in engagement with the contact 25, to move out of engagementwith the 4 contact 25, whereupon the motor operates at its high speed.

During operation of the truck, the speed of the motor can be changed atany time by shifting the member 26 to bring the lug 44 or into or out ofengagement with the contact 25. The grounding member 26 is preferablyprovided with a flange 46 that closely overlies the fiat top face of theinsulating block 22 so as to insure proper positioning of the contactportions of the member 26 with the energizing contacts.

Referring to Fig. '7 of the drawings, the solenoids I2' and I3 controlnormally open switches 41 and 4B and the speed control solenoid I5operates a normally closed switch 49 which normally short circuits theresistance I4 but which when opened connects the resistance in the motorcircuit to slow down the motor. a Current is supplied to the motor froma battery 50 through the conductor cable 8 and safety switch 9. Theswitch 9 is connected to the control solenoids I2 and I3 by means ofwires 5I,52 and 53, the wire 52 being also connected to the resistance[4. The terminals of the switch 49 are connected to opposite terminalsof the resistance I4 by means of wires 54 and 55 and a wire 56 connectsthe resistance I4 to one terminal of each of the switches 41 and 48, theopposite terminals of the switches 41 and 48 being connected by wires 51and 58 to forward and reverse windings 59 and 60 of the motor 4,. Whenthe grounding member '26 is moved'outwardly to engage the portion 42there-- of with the contact 23, the current passes through wires 5I,52-and 53, solenoid I2 and wire I6 to ground to energize the solenoid I2to close the switch 41. Upon closing of the switch 41 current can flowthrough the wires 51, 52, resistance I4, wire 56, switch 41, wire 51 andwinding 59 to ground. The resistance I4 is normally short circuited bywires 54, switch 49 and wires 55 and 56, but since the lug 44 engagesthe contact 25 at the same time that the contact portion 42 engages thecontact 23, the-motor is started at slow speed with the resistance I4 inseries with the winding 59. Upon further outward movement of thegrounding member 26, the lug 44 is moved out of engagement with contact25 to deenergize the solenoid I5 and permit the switch 49 to close,short circuiting the resistance I4 so that the motor will operate at ahigher speed. When the grounding member 26 is moved inwardly the contactportions 43 and the lug 45 simultaneously engage the contacts 24 and 25,energizing the solenoids I3 and I5 to connect the winding 60 in serieswith the resistance I4 to start the motor in reverse direction at lowspeed.

' In operating the motor to propel the truck either forwardly orrearwardly, the operator can change the speed at will during operation,but the motor is always started at slow speed and is always slowed downbefore it is stopped. By combining the change speed control with themotor starting and stopping devices on the draft tongue, the operatormay control the speed of the motor with the draft tongue 6 in any of itsinclined positions.

Trucks of the type herein disclosed have been found to be very usefulfor handling material in restricted spaces in warehouses, factories andthe like and in such spaces it is often necessary to hold the drafttongue in nearly vertical position in making short turns. It isadvantageous, there fore, to provide a control for the motor which willpermit operation at the desired speed in substantially all angularpositions of-the draft tongue.

It is to be understood that variations and modiflcations of the specificdevice herein shown and described for purposes of illustration may bemade without departing from the spirit of the invention.

What I claim is:

1. In a truck of the character described, an electric truck propellingmotor having forward and reverse windings, a resistance in series withsaid windings, means including a normally closed switch for shortcircuiting said resistance, a manually operable control member mountedfor movement away from and back to a neutral position, spring meansbiasing said member toward neutral position, means controlled by saidmember when moved in one direction from neutral position to energize oneof said windings and when moved in the opposite direction to energizethe other of said windings, and means controlled by said member whenmoved in either direction from neutral position to first open saidswitch to connect said resistance in the circuit of the energized motorwinding to operate the motor at slow speed and then to close said switchto short circuit said resistance to increase the speed of the motor,said switch being reopened to reinsert said resistance in the circuit ofthe energizing winding during the return movement of said member toreduce the speed of the motor prior to stopping.

2. In a truck of the character described, a truck propelling motorhaving forward and reverse windings, a resistance in series with saidwindings, means including a normally closed switch for short circuitingsaid resistance, a controller including a hand grip member movable inopposite directions from a neutral position to energize the forward andreverse windings of the motor, and means controlled by said manuallyoperable means upon movement in either direction from its neutralposition to first open said switch to connect said resistance in thecircuit of the energized motor winding to start themotor at slow speedand for then closing said switch to short circuit said resistance toincrease the speed of the motor and upon return movement in eitherdirection to open said switch to reconnect said resistance to theenergized winding to reduce speed prior to deenergization of the motor.

3. In a truck of the character described, a reversible electric truckpropelling motor, two starting solenoids, one controlling forwardactuation and the other rearward actuation of the motor, a thirdsolenoid controlling the speed of said motor, circuits for saidsolenoids including a contact for energizing each solenoid, and amanually operable controller engageable with said contacts, saidcontroller operating upon movement in either direction from a neutralposition to energize one or the other of the starting solenoids and toenergize and then deenergize the speed control solenoid.

IRVIN F. SCHRECK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,432,831 Blood Oct. 24, 19221,942,587 Whitman Jan. 9, 1934 2,108,607 Nelson Feb. 15, 1938 2,193,268Catron et al Mar. 12, 1940 2,209,356 Schreck July 30, 1940 2,327,583Framhein Aug. 24, 1943 2,399,605 Schroeder Apr. 30, 1946 2,401,113Schroeder May 28, 1946

